package com.bowlong.concurrent;

import java.io.Serializable;
import java.util.AbstractSet;
import java.util.Iterator;
import java.util.concurrent.ConcurrentHashMap;
import java.util.concurrent.ConcurrentMap;

public final class ConcurrentSet<E> extends AbstractSet<E> implements
		Serializable {

	private static final long serialVersionUID = -6761513279741915432L;

	private final ConcurrentMap<E, Boolean> map;

	/**
	 * Creates a new instance which wraps the specified {@code map}.
	 */
	public ConcurrentSet() {
		map = newConcurrentHashMap();
	}

	static <K, V> ConcurrentMap<K, V> newConcurrentHashMap() {
		return new ConcurrentHashMap<K, V>();
	}

	@Override
	public int size() {
		return map.size();
	}

	@Override
	public boolean contains(Object o) {
		return map.containsKey(o);
	}

	@Override
	public boolean add(E o) {
		return map.putIfAbsent(o, Boolean.TRUE) == null;
	}

	@Override
	public boolean remove(Object o) {
		return map.remove(o) != null;
	}

	@Override
	public void clear() {
		map.clear();
	}

	@Override
	public Iterator<E> iterator() {
		return map.keySet().iterator();
	}
}
